Here Lewis sets up what has come to be called "Lewis's Trilemma": that Christ was either the Son of God as He claimed, a madman, or "the Devil of Hell." He based this statement on what he had already said about Christ's self-descriptions (see Bookmark for page 51). In Lewis's opinion, "What this man said was, quite simply, the most shocking thing that has ever been uttered by human lips" (page 51).

Understandably, the "trilemma" has created controversy. Some say Christ never claimed to be the Son of God; however, various New Testament passages contradict that statement.

Lewis uses the same logic in chapter five of The Lion, the Witch and the Wardrobe when Susan and Peter disbelieve Lucy's story about finding Narnia: "There are only three possibilities. Either your sister is telling lies, or she is mad, or she is telling the truth. You know she doesn't tell lies and it is obvious that she is not mad. For the moment then and unless any further evidence turns up, we must assume that she is telling the truth" (The Chronicles of Narnia [New York: HarperCollins, 2001], page 131).